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Demand controlled recirc/purge


markocosic

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Hot water recirculation is nice but (can be) wasteful.

 

You could recirculate only when there is presence detected. That's nice. Any tried tested and recommended presence sensors for (a) whole bathroom or (b) right next to kitchen sink?

 

You could recirculate right back to the cold feed to the tank.

 

You could also backfeed the cold water line near the fixture back towards the tank.

 

See the last bit of this YouTube. Is that legal under UK regs? @Nickfromwales?

 

It look neat to avoid an unnecessary return line; at the expense of your cold water being lukewarm afterwards.

 

 

This also worth a read:

 

https://www.garykleinassociates.com/PDFs/15 - Efficient Hot-Water Piping-JLC.pdf

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12 hours ago, markocosic said:

You could also backfeed the cold water line near the fixture back towards the tank.

 

See the last bit of this YouTube. Is that legal under UK regs? @Nickfromwales?

 

It look neat to avoid an unnecessary return line; at the expense of your cold water being lukewarm afterwards


No no no no !!!!! That’s not legal and you are not allowed to push water back into the cold feed..!!!! That’s proper dumb American plumbing .. 

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What distances are your taps from the UVC?

 

We have a 10mm Hep20 to the kitchen tap fed from a manifold preheated by convection.  The pipe length is 13m from memory. Time to hot is 8-9 seconds and flow rate is 5l/min. About 2-3 seconds of this delay is the tap itself and the monobloc looses about 1l/min flow rate too. 

 

If you can position your UVC near the kitchen tap and toilet basins a circulation loop is unneeded IMO. 

 

 

 

 

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Nothing specific in mind - it just seemed such a simple solution to existing setups that there must be a catch.

 

Cooler water would recirculate back towards the unvented cylinder/expansion vessel before being sucked back towards the fixture to blend with the hot.

 

What's the UK logic for prohibiting it? Risk is...?

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I second the 10mm pipes. Less than 10seconds for hot water. 

 

I also fully insulated the got water pipe to the main kitchen tap. So if your in the kitchen and constantly using hot wat on and off, you don't need flush out all the water in the pipe as it stays warm for a good 15mins.

Edited by Conor
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  • 4 months later...
On 30/09/2022 at 23:47, markocosic said:

Any tried tested and recommended presence sensors for (a) whole bathroom or (b) right next to kitchen sink?

 

Seems like a Grundfos pump is the way to go but I can't figure out if/how to trigger via a relay or other external controller. Is that possible?

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